I think that, once you're going that far back in history, it's pretty critical to keep track of the GNU/Linux distinction. Linus just wrote a kernel. And then the GNU userland, which had already been in development since the mid 80s, but was still somewhat lacking a workable kernel, was adopted as the official userland to use with the Linux kernel.

And at roughly the same time, IIRC, when Sun decided to migrate their Unix from a BSD flavor to a SysV flavor, which came to be called Solaris, they also used some GNU bits. Which might explain some similarities between the two.

Illumos and friends are effectively dead, except as hobbies for enthusiasts. Sun Microsystems, now Oracle, didn't like the reception Open Solaris got so they packed up their source code and went home.

Which is really a shame.

All 'True' Unixes are just closed source versions of what originally were open source operating systems. By taking copyright seriously and having the misconception that there is intrinsic value in 'IP' they effectively sentenced their operating systems and investors to a long term grave.

But I doubt most of them feel bad about it. They got their millions and their nice fat retirements. It doesn't matter now if customers now view their once dominate systems as a sort of technical debt cancer.

If it wasn't for the destructive power that copyright has on technology and the demands of board members to monetize Unix.. we would all be using BSD right now. Unfortunately the tech people from 30 years ago didn't understand the power of 'letting go' and thus allowed them to destroy Unix.

As far as docker goes it has a lot of momentum as a daemon and it'll probably stay that way for a long time despite some technically superior solutions for running containers that have cropped up in the past few years. The newer container solutions just don't have the community backing them and that matters.